1. Field of the Invention
The present invention relates generally to wireless (e.g., cellular) telecommunication networks and, more specifically, to controlling network services or features to which a roaming user has access.
2. Description of the Related Art
The term “roaming” refers to a user (also referred to as a subscriber) operating a cellular telephone or other mobile station on a wireless network other than that operated by the carrier to whose services the user subscribes (via a subscription agreement, etc.). The network operated by the user's carrier is sometimes referred to with respect to a user as the “home network,” and the network on which the user is roaming is sometimes referred to as the “visited network.” The carrier that operates the home network typically has contractual “roaming agreements” with other carriers (sometimes referred to as roaming partners) that allow each carrier's subscribers to roam on the other's network.
When a mobile station initially moves into or powers-up in a network other than the home network and detects a signal that indicates the visited network may be one in which the mobile station can operate, the mobile station attempts to register with the visited network. A registration involves an exchange of messages between the Home Location Register (HLR), which is part of the home network, and a Visitor Location Register (VLR), which is part of the visited network. Specifically, in networks that conform to the Global System for Mobile telecommunications (GSM) standard, the VLR sends an Update Location (UL) message to the home network, indicating the identity of the visiting mobile station and requesting subscriber data relating to that mobile station. In response to the UL message, the HLR sends an Insert Subscriber Data (ISD) message to the visited network. The ISD message contains subscriber information that indicates, among other things, the services to which the roaming mobile station is to have access.
A carrier may offer a variety of network-based “services” (also referred to as “features”) to which a customer can subscribe or otherwise be given access in addition to the basic service of wireless voice telephony using the home network. The act of the carrier giving (or restricting) access to selected services and setting data values relating to such selected services is commonly referred to as “provisioning” the subscriber's account. Common examples of services include voicemail, calling line identification, call forwarding, call waiting, text messaging, Internet access, international roaming, pre-paid roaming, call blocking, etc. While some services are common and supported by many networks, other services are not. Thus, while a subscriber may have access to all services covered by the subscription when operating on the home network, the subscriber may have access to fewer services when roaming.
The logic by which a conventional HLR operates is typically embodied in a single table that lists each subscriber (e.g., by International Mobile Station Identification number) and a corresponding list of services. For convenience, the HLR table may designate each subscriber as either an “Entitlement” (E) subscriber or “Restriction” (R) subscriber. The services listed as corresponding to an E subscriber are those to which the subscriber's mobile station is to have access; the mobile station is not to have access to any services that are not listed. The services listed as corresponding to an R subscriber are those to which the subscriber's mobile station is to be restricted from accessing; the mobile station is to have access to all other services that are supported but not listed. The E/R designation is commonly believed to be more efficient than, for example, listing in all cases all services to which subscribers are to have access or listing in all cases all services from which subscribers are to be restricted from accessing. For example, in a case in which a subscriber is to have access to only a single service, it is more efficient to designate the subscriber as an E and list the single feature than to designate the subscriber as an R and list dozens of features. However, in a case in which a subscriber is to have access to a package or bundle of many services, it is more efficient to designate the subscriber as an R and list only the few to which the subscriber is not to have access.
The issue of subscribers having access to fewer services while roaming than while operating on the home network has been addressed in part by CAMEL, which is an acronym for Customized Applications for Mobile-Network Enhanced Logic. CAMEL is a protocol that allows roaming subscribers to access intelligent network features, such as voicemail and conditional call forwarding, to which they subscribe on their home network but that might otherwise not be supported by a visited network. CAMEL works by directing requests for such services back to the home network, which provides the logic for operating the service. When a mobile station registers in a system that supports CAMEL, the ISD message that the HLR sends includes Originating CAMEL Subscription Information (OCSI), identifying the services that are supported via CAMEL and providing related parameters. The VLR responds to the ISD message with an Insert Subscriber Data Result (ISDR) message, indicating whether the visited network supports the feature. In this manner, the set of features accessible to the roaming mobile station is established.
In some cases, the set of features accessible to the mobile station is further limited by the home network. For example, even though a subscriber may have access to service “A” on the home network (and in some instances certain other networks), the carrier may prevent the subscriber from having access to service “A” on another network because the carrier believes its roaming partner does not properly support service “A” on its network. Some services involve more parameters than simply providing such a service or not, and a carrier may believe that if the other network does not or cannot set the parameters in the same way as the carrier, that the subscriber should simply be denied access to that service when visiting the other network. For example, a carrier may allow a user to access CAMEL service when roaming on network “X” but entirely prevent the user from accessing CAMEL service when roaming on network “Y” simply because network “Y” does not utilize one or more of the CAMEL parameters in the way the carrier deems proper.
In summary, the set of services accessible to a roaming mobile station is limited by: (a) the set of services for which the mobile station is provisioned, i.e., to which the subscriber subscribes; (b) the set of services that the visited network supports; and (c) the set of services that the home network permits the mobile station to access on the visited network. The logic that is conventionally employed to determine the set of services to which a roaming subscriber is to have access is essentially no more complex than such a logical “AND” operation among (a), (b) and (c).